Rigid electro-optic device using a transparent ferroelectric ceramic element

Abstract

A rigidly bonded electro-optic phase retardation device comprising a transparent, electrically induced ferroelectric ceramic element bonded with a rigid adhesive in sandwich-like configuration between transparent sheet elements, such as glass, or polarizer elements is described. The electro-optic phase retardation device, provided with means for applying an electric field across at least a portion of the induced ferroelectric ceramic element, can be utilized as a birefringent optical device for controllable modulation of polarized light passing through the device. The device is bonded with an adhesive material, such as a cross-linked unsaturated polyester, effective to provide a rigid boundary between the ceramic material and the sheet elements thereof and exhibits rapid optical response speed in the switching from a field-induced birefringent mode to an isotropic zero-field condition. The device is thus suited to application in welding plates, glasses, goggles, helmets and similar devices for controlling the transmission of light radiations to the wearer's eyes, particularly in the prevention of flashblindness.

What is claimed is: 
     
       1. An electro-optic phase retardation device comprising an optically transparent lanthanum-modified lead zirconate titanate electro-optic ceramic element exhibiting substantially isotropic properties in a quiescent state and quadratic electro-optic properties in a field-induced state, said electro-optic ceramic element having substantially parallel optical quality surfaces, electrode means for applying an electric field to said electro-optic ceramic element in a plane normal to the direction of propagation of light through the electro-optic device; and isotropic sheet elements bonded to said electro-optic ceramic element in sandwich-like configuration with an adhesive effective to provide a rigid boundary between the interfaces of said ceramic electro-optic element and isotropic sheet elements. 
     
     
       2. The electro-optic phase retardation device of claim 1 wherein the isotropic sheet elements adhesively bonded to said electro-optic ceramic element comprise sheets of glass. 
     
     
       3. The electro-optic phase retardation device of claim 2 wherein the electro-optic ceramic element is a lanthanum-modified lead zirconate-titanate exhibiting slim-loop hysteresis properties and has a coercive field of about zero. 
     
     
       4. The electro-optic phase retardation device of claim 3 wherein the electro-optic ceramic element is a lanthanum-modified lead zirconate-titanate having the formula (Pb 1-x  La x ) (Zn y  Ti z ) 1-x/4  O 3 , wherein the ratio of y/z is in the range of from about 5/95 to about 90/10 and wherein x is in the range of from about 9 to about 25 atom percent. 
     
     
       5. The electro-optic phase retardation device of claim 4 wherein the ratio of y/z is about 65/35 and x is in the range of about 9 to about 12. 
     
     
       6. The electro-optic phase retardation device of claim 1 wherein said means for applying an electric field to said ceramic element comprises metallic electrodes on at least one of said optical quality surfaces. 
     
     
       7. The electro-optic phase retardation device of claim 6 wherein said means for applying an electric field to said ceramic element comprises a plurality of interdigital electrodes extending across substantially the entire area of each of said optical quality surfaces. 
     
     
       8. The electro-optic phase retardation device of claim 7 wherein the electro-optic ceramic element is a lanthanum-modified lead zirconate-titanate exhibiting slim-loop hysteresis properties and has a coercive field of about zero. 
     
     
       9. The electro-optic phase retardation device of claim 8 wherein the ceramic element is a lanthanum-modified lead zirconate-titanate having the formula (Pb 1-x  La x ) (Zn y  Ti z ) 1-x/4  O 3  wherein the ratio of y/z is in the range of from about 5/95 to about 90/10 and wherein x is in the range of from about 9 to about 25 atom percent. 
     
     
       10. The electro-optic retardation device of claim 9 wherein the glass elements are bonded to said electro-optic ceramic element with an adhesive comprising a cross-linked polyester of an unsaturated dibasic acid and a dihydric alcohol. 
     
     
       11. The electro-optic phase retardation device of claim 9 wherein the adhesive comprises a styrene cross-linked polyester of maleic acid and ethylene glycol. 
     
     
       12. The electro-optic phase retardation device of claim 1 wherein the adhesive comprises a layer of about 0.02 mm. to about 0.13 mm. thickness. 
     
     
       13. An electro-optic phase retardation device comprising an optically transparent lanthanum-modified lead zirconate-titanate electro-optic ceramic element exhibiting substantially isotropic properties in a quiescent state and quadratic electro-optic properties in a field-induced state, said electro-optic ceramic element having substantially parallel optical quality surfaces, electrode means for applying an electric field to said electro-optic ceramic element in a plane normal to the direction of propagation of light through the electro-optic device, and polarizer elements bonded to said electro-optic ceramic element in sandwich-like configuration with an adhesive effective to provide a rigid boundary between the interfaces of said electro-optic ceramic element and said polarizer elements. 
     
     
       14. The electro-optic phase retardation device of claim 13 wherein the polarizer elements are comprised of polymeric light-polarizing sheet materials. 
     
     
       15. The electro-optic phase retardation device of claim 14 wherein the light-polarizing sheet elements are oriented with their polarization axes in perpendicular planes. 
     
     
       16. The electro-optic phase retardation device of claim 15 wherein the electro-optic ceramic element is a lanthanum-modified lead zirconate-titanate exhibiting slim-loop hysteresis properties and has a coercive field of about zero. PG,30 
     
     
       17. The electro-optic phase retardation device of claim 16 wherein the electro-optic ceramic element is a lanthanum-modified lead-zirconate-titanate having the formula (Pb 1-x  La x ) (Zr y  Ti z ) 1-x/4  O 3  wherein the ratio of y/z is in the range of from about 5/95 to about 90/10 and wherein x is in the range of from about 9 to about 25 atom percent. 
     
     
       18. The electro-optic phase retardation device of claim 17 wherein the ratio of y/z is about 65/35 and x is in the range of about 9 to about 12. 
     
     
       19. The electro-optic phase retardation device of claim 13 wherein the polarizer elements are bonded to said electro-optic ceramic element with an adhesive comprising a cross-linked polyester of an unsaturated dibasic acid and a dihydric alcohol. 
     
     
       20. The electro-optic retardation device of claim 19 wherein the adhesive comprises a styrene cross-linked polyester of maleic acid and ethylene glycol. 
     
     
       21. The electro-optic phase retardation device of claim 13 wherein a transparent glass sheet element is bonded to each of said polarizer elements. 
     
     
       22. The electro-optic phase retardation device of claim 13 wherein said means for applying an electric field to said ceramic element comprises metallic electrodes on at least one of said optical quality surfaces. 
     
     
       23. The electro-optic phase retardation device of claim 22 wherein said means for applying an electric field to said ceramic element comprises a plurality of interdigital electrodes extending across substantially the entire area of each of said optical quality surfaces. 
     
     
       24. The electro-optic phase retardation device of claim 23 wherein the electro-optic ceramic element is a lanthanum-modified lead zirconate-titanate exhibiting slim-loop hysteresis properties and has a coercive field of about zero. 
     
     
       25. The electro-optic phase retardation device of claim 24 wherein the electro-optic ceramic element is a lanthanum-modified lead zirconate-titanate having the formula (Pb 1-x  La x ) (Zr y  Ti z ) 1-x/4  O 3  wherein the ratio of y/z is in the range of from about 5/95 to about 90/10 and wherein x is in the range of from about 9 to about 25 atom percent. 
     
     
       26. The electro-optic phase retardation device of claim 25 wherein said polarizer elements are bonded to said electro-optic ceramic element with an adhesive comprising a cross-linked polyester of an unsaturated dibasic acid and a dihydric alcohol. 
     
     
       27. The electro-optic phase retardation device of claim 26 wherein the adhesive comprises a styrene cross-linked polyester of maleic acid and ethylene glycol. 
     
     
       28. The electro-optic phase retardation device of claim 27 wherein a transparent glass sheet element is bonded to each of said polarizer elements. 
     
     
       29. The electro-optic phase retardation device of claim 13 wherein the adhesive comprises a layer of from about 0.02 mm. to about 0.13 mm. thickness.